I have tested 4 consistent results over a period of three years in my studies of my personal MBTI psychometric profile. The first time I was typed was by my brother. He typed me an INTJ. I was interested so I studied deeper into MBTI ending up choosing INTJ as my own assessment of my type. I had not yet taken an MBTI test nor was I in a deeper understanding of the functions. Taking the MBTI test for the first time, INTJ was my result. Over a period of time and many different tests I have received INTJ, INTP, INFJ and INFP the majority being INTJ. Although I had little doubt of my type I was curious to the possible reasons for the errors going far enough to dub me INFP. So I learnt about functions in which I understood why such is possible. With 3 introverted functions used as the most common of my personal functions use, it would not come to much surprise.

The MBTI tests can be very worthless by perception of the person taking the test and by the clumsily written wordings of the test by the test maker and/or misinterpretation of the test taker. Both instill it's own addition to the margin of error and yet are not the only factors that may cause errors of a wrong result in an MBTI test.

I've tested as 14 different types.. never ISFJ or ESFJ, but all the others, yeah. Usually I've needed just a slightly different mindset to genuinely score as a different type. That's the thing with the typology system: deviate ever so slightly from the XXXX type, and you will score as anything. Scoring 51% or 49% on any scale will make all the difference.